Dust collected in New Orleans homes mold-contaminated because of the flooding after hurricane Katrina was analyzed for molds and mycotoxins. The mycoflora was studied by cultivation and quantitative PCR for selected molds. The most commonly found mold taxa were Aspergillus, Cladosporium, and Penicillium. Verrucarol, a hydrolysis product of macrocyclic trichothecenes predominately produced by Stachybotrys spp. was identified in three dust samples by gas chromatography-tandem mass spectrometry, and sterigmatocystin (produced by various Aspergillus spp.) was found in two samples by high pressure liquid chromatography-tandem mass spectrometry. This is the first demonstration of mycotoxins in Katrina-associated dust samples. The analytical methods used represent valuable tools in further studies on bioaerosol exposure and health risks.

Qualitative reporting of home indoor moisture problems predicts respiratory diseases. However, causal agents underlying such qualitative markers remain unknown. In the homes of 198 multiple allergic case children and 202 controls in Sweden, we cultivated culturable fungi by directly plating dust, and quantified (1-3, 1-6)-β-d-glucan and ergosterol in dust samples from the child's bedroom. We examined the relationship between these fungal agents and degree of parent or inspector-reported home indoor dampness, and microbiological laboratory's mold index. We also compared the concentrations of these agents between multiple allergic cases and healthy controls, as well as IgE-sensitization among cases. The concentrations of culturable fungal agents were comparable between houses with parent and inspector-reported mold issues and those without. There were no differences in concentrations of the individual or the total summed culturable fungi, (1-3, 1-6)-β-d-glucan, and ergosterol between the controls and the multiple allergic case children, or individual diagnosis of asthma, rhinitis, or eczema. Culturable fungi, (1-3, 1-6)-β-d-glucan, and ergosterol in dust were not associated with qualitative markers of indoor dampness or mold or indoor humidity. Furthermore, these agents in dust samples were not associated with any health outcomes in the children.

The principle objective of the Danish research program 'Indoor Environment and Children's Health' (IECH) was to explore associations between various exposures that children experience in their indoor environments (specifically their homes and daycare centers) and their well-being and health. The targeted health endpoints were allergy, asthma, and certain respiratory symptoms. The study was designed with two stages. In the first stage, a questionnaire survey was distributed to more than 17000 families with children between the ages of 1 and 5. The questionnaire focused on the children's health and the environments within the homes they inhabited and daycare facilities they attended. More than 11000 questionnaires were returned. In the second stage, a subsample of 500 children was selected for more detailed studies, including an extensive set of measurements in their homes and daycare centers and a clinical examination; all clinical examinations were carried out by the same physician. In this study, the methods used for data collection within the IECH research program are presented and discussed. Furthermore, initial findings are presented regarding descriptors of the study population and selected characteristics of the children's dwellings and daycare centers. Practical Implications: This study outlines methods that might be followed by future investigators conducting large-scale field studies of potential connections between various indoor environmental factors and selected health endpoints. Of particular note are (i) the two-stage design - a broad questionnaire-based survey followed by a more intensive set of measurements among a subset of participants who have been selected based on their responses to the questionnaire; (ii) the case-base approach utilized in the stage 2 in contrast to the more commonly used case-control approach; (iii) the inclusion of the children's daycare environment when conducting intensive sampling to more fully capture the children's total indoor exposure; and (iv) all clinical examinations conducted by the same physician. We recognize that future investigators are unlikely to fully duplicate the methods outlined in this study, but we hope that it provides a useful starting point in terms of factors that might be considered when designing such a study.

Particle mass and number concentrations were measured in a mechanically ventilated classroom as part of a study of ventilation strategies for energy conservation. The ventilation system was operated either continuously, intermittently, or shut down during nights while it was on during workdays. It appears that the nighttime ventilation scheme is not important for indoor particle concentrations the following day if fans are operated to give five air exchanges in advance of the workday. The highest concentrations of PM10 were found during and after workdays and were due to human activity in the classroom. The average workday PM10 concentration was 14 μg/m(3) , well below the WHO guideline values. The number concentration of particles with diameter <0.750 μm was typically between 0.5 × 10(3) and 3.5 × 10(3)  particle/cm(3) . These concentrations were largely independent of the occupants. Transient formation of small particles was observed when ventilation was shut down. Then remaining ozone reacted with terpenes emitted by indoor sources and gave up to 8 × 10(3)  particle/cm(3) before formation stopped due to lack of ozone. The intermittent ventilation regime was found least favorable for the indoor air quality in the classroom.

Toxic microbial secondary metabolites have been proposed to be related to adverse health effects observed in moisture-damaged buildings. Initial steps in assessing the actual risk include the characterization of the exposure. In our study, we applied a multi-analyte tandem mass spectrometry-based methodology on sample materials of severely moisture-damaged homes, aiming to qualitatively and quantitatively describe the variety of microbial metabolites occurring in building materials and different dust sample types. From 69 indoor samples, all were positive for at least one of the 186 analytes targeted and as many as 33 different microbial metabolites were found. For the first time, the presence of toxic bacterial metabolites and their co-occurrence with mycotoxins were shown for indoor samples. The bacterial compounds monactin, nonactin, staurosporin and valinomycin were exclusively detected in building materials from moist structures, while chloramphenicol was particularly prevalent in house dusts, including settled airborne dust. These bacterial metabolites are highly bioactive compounds produced by Streptomyces spp., a group of microbes that is considered a moisture damage indicator in indoor environments. We show that toxic bacterial metabolites need to be considered as being part of very complex and diverse microbial exposures in ’moldy’ buildings. Practical Implications: Bacterial toxins co-occur with mycotoxins in moisture-damaged indoor environments. These compounds are measurable also in settled airborne dust, indicating that inhalation exposure takes place. In attempts to characterize exposures to microbial metabolites not only mycotoxins but also bacterial metabolites have to be targeted by the analytical methods applied. We recommend including analysis of samples of outdoor air in the course of future indoor assessments, in an effort to better understand the outdoor contribution to the indoor presence of microbial toxins. There is a need for a sound risk assessment concerning the exposure to indoor microbial toxins at concentrations detectable in moisture-damaged indoor environments.

We spend most of our time indoors; however, little is known about the effects of exposure to aerosol particles indoors. We aimed to determine differences in relative toxicity and physicochemical properties of PM2.5 collected simultaneously indoors (PM2.5 INDOOR) and outdoors (PM2.5 OUTDOOR) in 15 occupied homes in southern Sweden. Collected particles were extracted from filters, pooled (indoor and outdoor separately), and characterized for chemical composition and endotoxins before being tested for toxicity in mice via intratracheal instillation. Various endpoints including lung inflammation, genotoxicity, and acute-phase response in lung and liver were assessed 1, 3, and 28 days post-exposure. Chemical composition of particles used in toxicological assessment was compared to particles analyzed without extraction. Time-resolved particle mass and number concentrations were monitored. PM2.5 INDOOR showed higher relative concentrations (μg mg−1) of metals, PAHs, and endotoxins compared to PM2.5 OUTDOOR. These differences may be linked to PM2.5 INDOOR causing significantly higher lung inflammation and lung acute-phase response 1 day post-exposure compared to PM2.5 OUTDOOR and vehicle controls, respectively. None of the tested materials caused genotoxicity. PM2.5 INDOOR displayed higher relative toxicity than PM2.5 OUTDOOR under the studied conditions, that is, wintertime with reduced air exchange rates, high influence of indoor sources, and relatively low outdoor concentrations of PM. Reducing PM2.5 INDOOR exposure requires reduction of both infiltration from outdoors and indoor-generated particles. © 2022 The Authors.